1. Field of the Invention
The present invention relates generally to a unit with at least one plate made of a material which is permeable to thermal radiation, such as glass ceramic, glass, ceramic or a similar material, as a surface for cooking, frying and/or keeping warm. The unit is positioned on a frame construction and has different types of adjustable heat sources distributed underneath and on the plate. Some of the heat sources are distributed under the plate in the form of radiant burners and act indirectly by radiation through the plate. Other heat sources are located above the level of the plate in the form of open atmospheric or atmospheric pressure gas burners and transmit heat directly by producing open flames. The respective heat sources correspond to the cooking, frying and/or warming positions.
2. Background Information
Different heat sources on a cooking unit offer the user altogether different and specific advantages.
For example, the open gas flame of an atmospheric or atmospheric pressure gas burner is very much preferred for rapid browning, frying and sauteing. The atmospheric gas burner is also preferred when extended cooking is not desired.
On the other hand, electrically heated glass ceramic cooktops are prized for the precision with which the heat they produce can be regulated, their uniform temperature distribution and the ability to turn heating circuits on and off with great flexibility. This type of cooktop also includes gas radiant burners which provide heat through the plate indirectly by infrared radiation, as well as known induction cooktops.
A significant number of users could therefore benefit from the characteristics of both types of heat sources. The kitchen cooking appliance industry has responded to this demand by manufacturing combination units.
German Patent No. 30 49 491 C2, describes an oven, the top surface of the oven is formed by a heat transmitting plate, in particular a glass ceramic plate. The heat transmitting plate is formed by a single flat and completely closed surface, below which surface there is at least one gas radiant burner. There is at least one electrical radiant heating element located underneath the heat transmitting plate and outside the cooking area, next to and/or in the slow cooking or warming area.
German Patent No. 30 49 491 C2 describes units with gas radiant burners plus electrically powered radiant heating elements underneath a heat transmitting plate which has a completely closed surface.
French Patent No. 2 626 964 A1 describes an oven in which there is an electrical radiant heating element underneath a glass ceramic cover, as well as standard gas burners with an open flame. French Patent No. 2 626 964 A1 describes different types of heat sources, namely electrical radiant heating elements and open gas burners, whereby in this case the glass ceramic plate covers only the single electrical radiant heating element, and does not form a continuous plate with heat sources distributed underneath and/or on it.
German Patent No. 42 27 672 C2 discloses a cooking unit with a plate made of a material which is permeable to thermal radiation, such as glass ceramic. The cooking unit has different types of heat sources located underneath, in and/or on the plate. Some of the heat sources are infrared gas radiant burners distributed underneath the plate, which infrared gas radiant burners act indirectly through the plate by infrared radiation. Other heat sources are located above and/or at the level of the plate, and transmit heat directly by the generation of open flames in the form of atmospheric open gas burners.
Combination units which have both gas and electrically heated heat sources, are available both as stand-alone ovens and as built-in units.
For example, these types of ovens have a long and successful tradition in France.
In addition to the advantages of the different types of heat generation from the various heat sources, in the past and still to some extent today, the lack of complete security with regard to the supply of either gas or electricity to the heat source also plays a not insignificant role. If the electric power supply fails, for example, cooking can continue with the gas heat source, and conversely, if the gas tank is empty, cooking can continue on the electrically heated cooktop. Such cooking units conventionally consist of four cooking positions, whereby either two of the positions are heated electrically and two of the positions are heated with gas, or three of the positions are heated with gas and one position is heated electrically.
The electrically heated cooking positions, in particular, are covered by a glass ceramic plate, and the actual heating elements are installed underneath the glass ceramic plate.
The electrical heating devices used are radiant heating elements, heater bands, halogen heating elements and also induction heating elements.
Likewise, gas cooking positions can be covered by a glass ceramic plate, underneath which the gas radiant burners are mounted, often with a burner plate made of ceramic or other high-temperature resistant fibers.
Another type of gas cooking position consists of open atmospheric gas burners which are routed through borings in the glass ceramic and sealed in place.
To set the pots on these gas cooking positions, additional top grates, sometimes called pot holders, are necessary. The top grates provide a secure and stable base for the cookware and also guarantee a complete combustion of the gas by admitting a sufficient quantity of air.
In addition to all the advantages of these combined cooking units, however, there is a significant disadvantage, namely that the different working height of the gas cooking positions, which gas cooking positions are operated with open, atmospheric gas burners, which gas burners project above the level of the plate for the surface of the unit, compared to the electric cooking nosition or the gas cooking position with gas radiant burners, which positions are located underneath the plate, results in pots and pans having to be handled on different levels.